1. Field of the Invention
This invention relates to lasers and laser systems, and, in one aspect to a laser-device for producing a hole in skin through which blood may be withdrawn. In one particular aspect this invention relates to modifying the output profile of a laser beam to produce improved skin perforators.
2. Description or Related Art
Capillary blood sampling is a process for obtaining blood samples from the sub-dermal capillary beds of patients. A common method is to produce a small wound in the patient's skin using a sharp needle or small blade, called a blood lancet. Lancets are commonly used once and discarded. The lancet procedure produces a sharp, blood infected waste product which represents a risk to patients and health care workers, and which must be disposed of under carefully controlled conditions. In addition, the use of disposable blood lancets requires the health care providing organization to maintain a large inventory of disposable lancets. Certain lancet designs include an exposed point which produce significant fear and apprehension in patients who anticipated a painful experience. Although modem designs have attempted to eliminate such apprehension, reduction of patient discomfort would significantly increase the usefulness of new capillary sampling techniques.
Lasers typically have a light source for optical excitation, an active laser material, and a set of reflecting mirrors. Most solid state lasers have a design with a rod of laser crystal or glass material optically pumped by a high intensity lamp or set of LED arrays, with mirrors placed a distance from, or in contact with, or coated onto, the surfaces of the laser rod. One mirror has either a hole or a reduced reflectance relative to the other. Light is injected from the lamp or LED array into the laser material initiating the discharge of photons from dopants in the rod. These photons travel between the two mirrors producing light amplification. The amplified laser beam escapes the system through the hole or area of reduced reflectance. As an active medium various lasant materials are used to produce different wavelengths of laser light. These materials include, but are not limited to, rare- earth-doped oxide and fluoride laser crystals and glasses, e.g. yttrium-aluminum-garnet (YAG). Such crystals and glasses will be doped with impurities to fix the resultant wavelength of the laser. These traditional laser designs have precise mirrored surfaces. The reflective surfaces are usually made by coating the surfaces with several thin layers of dielectric material. If separate mirrors are used, they are placed precisely with respect to the optical axis of the laser rod and with respect to each other. The reflective mirror surfaces can be also produced by coating them onto the polished faces of a laser crystal.
Modal distribution is a property of projected light. A projection mode can be characterized by an angular direction vector in which light beams may travel with respect to some normal angle. The normal angle is defined usually as 0 degrees with respect to the optical axis of a system. The modal distribution of a system can be characterized by a set of angular vectors in which light travels upon output from the system. A low order distribution is one in which most of the energy in a light beam travels parallel or near to parallel with the optical axis. Most commonly available laser devices are designed to have a low order distribution of modes; i.e., most devices are designed so that light energy travels only in the 0th order mode (parallel to the normal vector) or within a small set of angular vectors surrounding the normal vector. A higher order distribution is one in which energy light travels at greater angles with respect to the optical axis.
Laser perforators are disclosed in U.S. Pat. No. 5,165,418, in Japanese patent 4,314,428, and in PCT patent application US93/10279. Certain lasers of the type described in these publications will typically exhibit a low order distribution of modes with radiant energy concentrated toward the center of the beam and, thus, the holes, or wounds, produced are relatively deep and penetrating with respect to the thickness of the skin. Such wounds are the shape of a champagne glass with a broad entrance wound and a longer slender stem. Blood is found to be available from the upper bowl portion of the wound, but little blood escapes from the lower portion, or stem, of the wound. A variety of low-order mode distribution lasers have been developed and are used in medical applications, such as eye surgery, tissue necrosis, and sensor probes.
There has long been a need to produce capillary blood samples without the production of hazardous waste products. There has long been a need to eliminate the use of disposable implements for performing such procedures while reducing worker exposure to infectious disease. There has long been a need to reduce patient discomfort and pain associated with capillary blood collection.